The rules for American football can get pretty complicated, but an abbreviated explanation for the yellow line might go something like this: The team that has

The rules for American football can get pretty complicated, but an abbreviated explanation for the yellow line might go something like this: The team that has the ball has four tries (i.e. downs) to advance the ball 10 yards. If the team that has possession is abl to advance the ball 10 yards or more within four tries, the marker is reset to the next 10 yards. That's why it's insufficient to mark the lines on the field: if I started at the 10 yard mark and advanced to the 12 yard mark, the line would have to be placed at the 22 yard mark. Painting lines would mean that the entire field would eventually have to be painted and unpainted. I love American football but it's pretty much an acquired taste (lots of stoppage time, tons of instant replay, incomprehesible rules, heart-breaking inconsistency in the officiating, etc.)